Летрозол: Қолданылуы, зерттеулер және қауіп-қатерлер

Breast cancer drug

Letrozole is approved by the United States Food and Drug Administration (FDA) for the treatment of local or metastatic breast cancer that is hormone receptor positive or has an unknown receptor status in postmenopausal women.

Tamoxifen is also used to treat hormonally responsive breast cancer, but it does so by interfering with the estrogen receptor. However, letrozole is effective only in post menopausal women, in whom estrogen is produced predominantly in peripheral tissues (i. e. in adipose tissue, like that of the breast) and a number of sites in the brain. In pre menopausal women, the main source of estrogen is from the ovaries not the peripheral tissues, and letrozole is ineffective. In the BIG 1–98 Study, of post menopausal women with hormonally responsive breast cancer, letrozole reduced the recurrence of cancer, but did not change survival rate, compared to tamoxifen.

Letrozole has been used for ovulation induction by fertility doctors since 2001, because it has fewer side effects than clomiphene (Clomid) and less chance of multiple gestation. A study of 150 babies following treatment with either letrozole alone or letrozole and gonadotropins presented at the American Society of Reproductive Medicine 2005 Conference found no difference in overall abnormalities but did find a significantly higher rate of locomotor and cardiac abnormalities among the group having taken letrozole compared to natural conception. A larger, follow up study with 911 babies compared those born following treatment with letrozole to those born following treatment with clomiphene. That study also found no significant difference in the rate of overall abnormalities, but found that congenital cardiac anomalies was significantly higher in the clomiphene group compared to the letrozole group. Despite this, India banned the usage of letrozole in 2011, citing potential risks to infants. In 2012, an Indian parliamentary committee said that the drug controller office colluded with letrozole's makers to approve the drug for infertility in India and also stated that letrozole's use for infertility was illegal worldwide; however, such off label uses are legal in many countries such as the US and UK.

Tests have shown that the efficacy of first trimester medical abortions (using misoprostol) can be improved by including letrozole in the drug regimen.

Letrozole is contraindicated in women having a pre menopausal hormonal status, during pregnancy and lactation.

The most common side effects are sweating, hot flushes, arthralgia (joint pain), and fatigue. Letrozole is sometimes used as a treatment for gynecomastia, although it is probably most effective at this if caught in an early stage (such as in users of anabolic steroids). Unreliable source: date=September 2012

Some studies have shown that letrozole can be used to promote spermatogenesis in male patients with nonobstructive azoospermia. Letrozole has also been shown to delay the fusing of the growth plates in mice. When used in combination with growth hormone, letrozole has been shown effective in one adolescent boy with a short stature. Letrozole has also been used to treat endometriosis. Also in a study on Uterine myoma the volume was successfully reduced by use of an aromatase inhibitor. Rapid onset of action and avoidance of initial gonadotropin flare with an aromatase inhibitor. Letrozole has been documented to be safe and effective for improving height and pubertal outcomes in children living with constitutional delay in growth and puberty, and is better than testosterone with regard to improvement in testicular volume and delaying bone age progression. This was documented in a meta analysis published by Dutta et al. which analyzed data from 7 different randomized controlled trials.